Solar thermal unit

ABSTRACT

Solar thermal units and methods of operating solar thermal units for the conversion of solar insolation to thermal energy are provided. In some examples, solar thermal units have an inlet, and a split flow of heat absorbing fluid to either side of the solar thermal unit, along a first fluid flow path and a second fluid flow path. Optionally, one or more photovoltaic panels can be provided as part of the solar thermal unit, which may convert solar insolation to electric power that may be used by a system connected to the solar thermal unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, claims priority to and thebenefit of, U.S. patent application Ser. No. 16/543,323 filed on Aug.16, 2019 entitled “SOLAR THERMAL UNIT,” which is a continuation of,claims priority to and the benefit of, U.S. patent application Ser. No.15/482,104 filed on Apr. 7, 2017 entitled “SOLAR THERMAL UNIT,” whichclaims priority to Provisional Application No. 62/319,721, filed Apr. 7,2016 entitled “SOLAR THERMAL UNIT.” The disclosures of theaforementioned Applications are incorporated herein by reference intheir entirety.

SUMMARY

The present technology provides solar thermal units and methods ofoperating solar thermal units. Solar thermal units of the presenttechnology are configured to convert solar insolation to thermal energy.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific examples have been chosen for purposes of illustration anddescription, and are shown in the accompanying drawings, forming a partof the specification.

FIG. 1 is a perspective view of one example of a solar thermal unit ofthe present technology.

FIG. 2 is an exploded view of the solar thermal unit of FIG. 1.

FIG. 3 is a cross-sectional side view of the solar thermal unit of FIG.1, showing the flow path of the heat absorbing fluid.

FIG. 4 is a cross-sectional side view of a portion of the solar thermalunit of FIG. 3, showing the flow path of the heat absorbing fluid.

FIG. 5 is a cross-sectional side view of a second example of a solarthermal unit of the present technology.

FIG. 6 is a cross-sectional side view of a third example of a solarthermal unit of the present technology.

FIG. 7 is a cross-sectional side view of a fourth example of a solarthermal unit of the present technology.

FIG. 8 is a graph of a non-linear temperature profile in the absorber asolar thermal unit of the present technology.

FIG. 9 is a graph of insolation versus time showing the results oftesting one example of a solar thermal unit of the present technology.

FIG. 10 is a diagram of a first system for generating liquid water fromair in which a solar thermal unit of the present technology may be used.

FIG. 11 is a diagram of a second system for generating liquid water fromair in which a solar thermal unit of the present technology may be used.

FIG. 12 is an exploded view of a fifth example of a solar thermal unitof the present technology.

FIG. 13 is a is a cross-sectional side view of the solar thermal unit ofFIG. 12, showing the flow path of the heat absorbing fluid.

FIG. 14 is a graph of the efficiency versus temperature above ambient ofthe fifth example of the solar thermal unit, at two different flowrates.

DETAILED DESCRIPTION

The terms “comprise” (and any form of comprise, such as “comprises” and“comprising”), “have” (and any form of have, such as “has” and“having”), “include” (and any form of include, such as “includes” and“including”), and “contain” (and any form of contain, such as “contains”and “containing”) are open-ended linking verbs. As a result, anapparatus that “comprises,” “has,” “includes,” or “contains” one or moreelements possesses those one or more elements, but is not limited topossessing only those elements. Likewise, a method that “comprises,”“has,” “includes,” or “contains” one or more steps possesses those oneor more steps, but is not limited to possessing only those one or moresteps.

Any embodiment of any of the apparatuses, systems, and methods canconsist of or consist essentially of—rather thancomprise/include/contain/have—any of the described steps, elements,and/or features. Thus, in any of the claims, the term “consisting of” or“consisting essentially of” can be substituted for any of the open-endedlinking verbs recited above, in order to change the scope of a givenclaim from what it would otherwise be using the open-ended linking verb.

The feature or features of one embodiment may be applied to otherembodiments, even though not described or illustrated, unless expresslyprohibited by this disclosure or the nature of the embodiments.

Some details associated with the embodiments described above and othersare described below.

Solar thermal units of the present technology convert solar insolationto thermal energy by transferring energy from sunlight to a heatabsorbing fluid that flows through the solar thermal unit. In at leastsome examples, solar thermal units of the present technology may beconfigured such that the temperature gradient increases along the depthof the solar thermal unit, in the direction that the heat absorbingfluid flows along either flow path from the inlet to the outlet. Thismay result in heat being substantially extracted or directed away fromthe upper layers of the system, such as a glazing layer that has contactwith ambient air, keeping such layers relatively cool. In contrast,conventional solar thermal units tend to have an outer surface that isvery hot. The configuration of the solar thermal unit may also result inheat from the solar insolation being directed to and retained in themost insulated areas of the unit, reducing radiative losses from theunit.

The present disclosure further provides an apparatus and method forgenerating energy and/or water with integrated solar thermal andphotovoltaic conversion devices. Merely by way of example, the inventionhas been applied to a solar module and water generation devices, but itwould be recognized that the invention has a much broader range ofapplicability.

FIGS. 1-4 illustrate one example of a solar thermal unit 100 of thepresent technology. The solar thermal unit 100 has a split-flow designhaving two fluid flow paths.

With respect to the first fluid flow path, on the right hand side ofsolar thermal unit 100, there is a first glazing layer 102 that has anouter surface 104 and an inner surface 106. The outer surface 104 of thefirst glazing layer 102 may be exposed to ambient air. The first fluidflow path of the solar thermal unit 100 also has a first porous lightabsorbing material layer 108, which is below and spaced apart from thefirst glazing layer 102. The first porous light absorbing material layer108 has a top surface 110, a thickness 112, and a bottom surface 114. Aheat absorbing fluid 116, or a portion thereof, may flow through thesolar thermal unit 100 along the first fluid flow path from the inlet120 to the outlet 122.

As shown, the first glazing layer 102 and the first porous lightabsorbing material layer 108 each have the same width W and length L1.In alternative examples, including as those shown in FIGS. 6 and 7, thefirst glazing layer may have a length L, which is greater that thelength L1 of the first porous light absorbing material layer 108, andwhich may extend across the length of both fluid flow paths.

When it enters the solar thermal unit 100 through inlet 120, the heatabsorbing fluid 116 may have an initial temperature, which may or maynot be equal to the temperature of the ambient air outside the solarthermal unit 100, depending upon the application. After entering thesolar thermal unit 100 through the inlet 120, at least part of the heatabsorbing fluid 116 may flow along a first portion 118 of the firstfluid flow path, which extends from the inlet 120 along the innersurface 106 of the first glazing layer 102. The heat absorbing fluid 116may flow along the entire length L1 of the inner surface 106 of thefirst glazing layer 102 as it flows along the first portion 118 of thefirst fluid flow path.

The flow path of the heat absorbing fluid 116 along the first portion118 of the first fluid flow path may be controlled by the structuregeometry of the inlet 120, and/or the overall solar thermal unit 100.For example, inlet 120 may include one or more nozzles through which theheat absorbing fluid 116 flows into the solar thermal unit 100. The oneor more nozzles may control the velocity and direction of the heatabsorbing fluid 116 as it flows along the first portion 118 of the firstfluid flow path. Alternatively, the solar thermal unit 100 may includeat least one an interstitial layer, as described below.

Additionally, within the first portion 118 of the first fluid flow path,the heat absorbing fluid 116 may be evenly distributed across the entirewidth W of the inner surface 106 of the first glazing layer 102. As ittravels along the first portion 118 of the first fluid flow path, theheat absorbing fluid 116 may collect heat from along the inner surface106 of the first glazing layer 102. The temperature of the heatabsorbing fluid 116 at the end of the first portion 118 of the firstfluid flow path may thus be greater than the initial temperature of theheat absorbing fluid 116 at inlet 120. The amount of the temperatureincrease may be dependent upon several factors, including the level ofinsolation, ambient temperature, and inlet temperature.

After flowing through the first portion 118 of the first fluid flowpath, the heat absorbing fluid 116 may then flow through a firsttransition 138 and then along a second portion 140 of the of the firstfluid flow path. The second portion 140 of the first fluid flow pathextends along the top surface 110 of the porous light absorbing materiallayer 108. At least a portion of the heat absorbing fluid 116 may flowalong the entire length L1 of the top surface 110 of the porous lightabsorbing material layer 108 as it flows along the second portion 140 ofthe of the first fluid flow path. Additionally, within the secondportion 140 of the of the first fluid flow path, the heat absorbingfluid 116 may be evenly distributed across the entire width W of the topsurface 110 of the porous light absorbing material layer 108. As ittravels along the second portion 140 of the of the first fluid flowpath, the heat absorbing fluid 116 may collect heat from along the topsurface 110 of the porous light absorbing material layer 108. Thetemperature of the heat absorbing fluid 116 at the end of the secondportion 140 of the first fluid flow path may thus be greater than thetemperature of the heat absorbing fluid 116 at the end of the firstportion 118 of the first fluid flow path, as well as being greater thanthe initial temperature of the heat absorbing fluid 116 at inlet 120.

After flowing through the second portion 140 of the of the first fluidflow path, the heat absorbing fluid 116 may then flow along a thirdportion 142 of the first fluid path, through the thickness 112 of theporous light absorbing material layer 108. The heat absorbing fluid 116may collect heat from within the first porous light absorbing materiallayer 108 as it flows along the third portion 142 of the first fluidpath. The temperature of the heat absorbing fluid 116 at the end of thethird portion 142 of the first fluid flow path may thus be greater thanthe temperature of the heat absorbing fluid 116 at the end of the secondportion 140 of the first fluid flow path, as well as being greater thanthe initial temperature of the heat absorbing fluid 116 at inlet 120.

After flowing through the third portion 142 of the of the first fluidflow path, the heat absorbing fluid 116 may then flow along a fourthportion 144 of the first fluid path, along the bottom surface 114 porouslight absorbing material layer 108 to the outlet 122, where the heatabsorbing fluid may exit the solar thermal unit 100. The heat absorbingfluid 116 may collect heat from the bottom surface 114 porous lightabsorbing material layer 108, The heat absorbing fluid 116 may collectheat from the bottom surface 114 of the first porous light absorbingmaterial layer 110, as well as from any other components, such as theinsulation layer 130, that it contacts as it flows along the fourthportion 144 of the first fluid path. The temperature of the heatabsorbing fluid 116 at the end of the fourth portion 144 of the firstfluid flow path may thus be greater than the temperature of the heatabsorbing fluid 116 at the end of the third portion 142 of the firstfluid flow path, as well as being greater than the initial temperatureof the heat absorbing fluid 116 at inlet 120.

The solar thermal unit 100 may also have an insulation layer 130, whichmay have at least a bottom 132 and a side wall 134. The sidewall 134 mayextend around the entire perimeter of the solar thermal unit 100. Theinsulation layer 130 may be below and spaced apart from the first porouslight absorbing material layer 108. The insulation layer 130 may beconfigured to provide a first flow channel 136 that forms part of thefourth portion 144 of the first fluid path. The fourth portion 144 ofthe first fluid path may flow along the first flow channel 136, beneaththe porous light absorbing material layer 108, to the outlet 122.

Further, with respect to the first fluid flow path 118, the solarthermal unit 100 may have one or more interstitial layers, such as firstinterstitial layer 124, between the first glazing layer 102 and thefirst porous light absorbing material layer 108. Interstitial layer 124may promote flow interaction with the first glazing layer 102 and resultin increased heat extraction from the first glazing layer 102. Asillustrated, the first interstitial layer 124 may be a glazing, and maybe made of the same material or a different material that the firstglazing layer 102, and/or may include one or more photovoltaic (PV)panels. The first interstitial layer 124 may have a top surface 126 anda bottom surface 128. The top surface 126 of the first interstitiallayer 124 is below and spaced apart from the inner surface 106 of thefirst glazing layer 102 and the bottom surface 128 of the firstinterstitial layer 124 is above and spaced apart from the top surface110 of the first porous light absorbing material layer 108.

In examples where the solar thermal unit 100 includes a firstinterstitial layer 124, the first transition 138 may include a turn inthe first fluid path, around an end 192 of the first interstitial layer124. As illustrated in FIGS. 3 and 4, the first glazing layer 102 has alength L₁, and the first interstitial layer 124 has a length that isless than the length of the first glazing layer 102. The shorter lengthof the first interstitial layer 124 creates a first gap 194 between theend 192 of the first interstitial layer 124 and the side wall 134 of theinsulation layer 130. The turn of the first transition 138 may redirectthe heat absorbing fluid 116 over an angle that may be up to about 180°,including being between about 90° and about 180°. The first interstitiallayer 124 may have a width that is equal to the width W of the firstglazing layer 102. In such an example, the first portion 118 of thefirst fluid path extends from the inlet 120 along the inner surface 104of the first glazing layer 102 between the inner surface 104 of thefirst glazing layer 102 and the top surface 126 of the firstinterstitial layer 124, and the second portion 140 of the first fluidpath extends between the bottom surface 128 of the first interstitiallayer 124 and the top surface 110 of the first porous light absorbingmaterial layer 108. The second portion 140 of the first fluid path maybe in contact with the bottom surface 128 of the first interstitiallayer 124, and may thereby collect heat from the first interstitiallayer 124.

In examples where the solar thermal unit 100 includes a firstinterstitial layer 124, the heat absorbing fluid may also extract heatfrom the interstitial layer 124 as it flows along the first fluid flowpath. For example, as the heat absorbing fluid 116 travels along thefirst portion 118 of the first fluid flow path, the heat absorbing fluid116 may collect heat from along the inner surface 106 of the firstglazing layer 102 and from the top surface 126 of the first interstitiallayer 124. Also, as it travels along the second portion 140 of the ofthe first fluid flow path, the heat absorbing fluid 116 may collect heatfrom along the bottom surface 128 of the first interstitial layer 124and along the top surface 110 of the porous light absorbing materiallayer 108. As discussed above, the temperature gradient of the heatabsorbing fluid 116 may increase as the heat absorbing fluid flows alongthe first fluid flow path from the inlet 120 to the outlet 122, and thetemperature of the heat absorbing fluid at the outlet 122 may be greaterthan the temperature of the heat absorbing fluid 116 at the inlet 120.

The second fluid flow path, on the left hand side of solar thermal unit100, may have the same set of components as the first fluid flow path,and may be a mirror image of the first fluid flow path. As shown, theleft hand side of solar thermal unit 100 includes second glazing layer146 that has an outer surface 148 and an inner surface 150. The outersurface 148 of the second glazing layer 146 may be exposed to ambientair. The left hand side of solar thermal unit 100 also has a secondporous light absorbing material layer 152, which is below and spacedapart from the second glazing layer 146. The second porous lightabsorbing material layer 152 has a top surface 154, a thickness 156, anda bottom surface 158. The heat absorbing fluid 116, or a portionthereof, may flow through the solar thermal unit 100 along the secondfluid flow path from the inlet 120 to the outlet 122. As shown, thesecond glazing layer 146 and the second porous light absorbing materiallayer 152 each have the same width W and length Lz.

As discussed above, when it enters the solar thermal unit 100 throughinlet 120, the heat absorbing fluid 116 may have an initial temperature.After entering the solar thermal unit 100 through the inlet 120, atleast part of the heat absorbing fluid 116 may flow along a firstportion 160 of the second fluid flow path, which extends from the inlet120 along the inner surface 150 of the second glazing layer 146. Theheat absorbing fluid 116 may flow along the entire length L2 of theinner surface 150 of the second glazing layer 146 as it flows along thefirst portion 160 of the second fluid flow path. Additionally, withinthe first portion 160 of the second fluid flow path, the heat absorbingfluid 116 may be evenly distributed across the entire width W of theinner surface 106 of the first glazing layer 102. As it travels alongthe first portion 160 of the second fluid flow path, the heat absorbingfluid 116 may collect heat from along the inner surface 150 of thesecond glazing layer 146. The temperature of the heat absorbing fluid116 at the end of the first portion 160 of the second fluid flow pathmay thus be greater than the initial temperature of the heat absorbingfluid 116 at inlet 120.

After flowing through the first portion 160 of the second fluid flowpath, the heat absorbing fluid 116 may then flow through a secondtransition 162 and then along a second portion 164 of the of the secondfluid flow path. The second portion 140 of the first fluid flow pathextends along the top surface 154 of the second porous light absorbingmaterial layer 152. At least a portion of the heat absorbing fluid 116may flow along the entire length L₁ of the top surface 154 of the secondporous light absorbing material layer 152 as it flows along the secondportion 164 of the of the second fluid flow path. Additionally, withinthe second portion 164 of the of the second fluid flow path, the heatabsorbing fluid 116 may be evenly distributed across the entire width Wof the top surface 154 of the porous light absorbing material layer 152.As it travels along the second portion 164 of the of the second fluidflow path, the heat absorbing fluid 116 may collect heat from along thetop surface 154 of the porous light absorbing material layer 152. Thetemperature of the heat absorbing fluid 116 at the end of the secondportion 164 of the second fluid flow path may thus be greater than thetemperature of the heat absorbing fluid 116 at the end of the firstportion 160 of the second fluid flow path, as well as being greater thanthe initial temperature of the heat absorbing fluid 116 at inlet 120.

After flowing through the second portion 164 of the of the second fluidflow path, the heat absorbing fluid 116 may then flow along a thirdportion 166 of the second fluid path, through the thickness 156 of thesecond porous light absorbing material layer 152. The heat absorbingfluid 116 may collect heat from within the second porous light absorbingmaterial layer 152 as it flows along the third portion 166 of the secondfluid path. The temperature of the heat absorbing fluid 116 at the endof the third portion 166 of the second fluid flow path may thus begreater than the temperature of the heat absorbing fluid 116 at the endof the second portion 164 of the second fluid flow path, as well asbeing greater than the initial temperature of the heat absorbing fluid116 at inlet 120.

After flowing through the third portion 142 of the of the second fluidflow path, the heat absorbing fluid 116 may then flow along a fourthportion 168 of the second fluid path, along the bottom surface 158 ofthe second porous light absorbing material layer 152 to the outlet 122,where the heat absorbing fluid 116 may exit the solar thermal unit 100.The heat absorbing fluid 116 may collect heat from the bottom surface158 of the second porous light absorbing material layer 152, as well asfrom any other components, such as the insulation layer 130, that itcontacts as it flows along the fourth portion 168 of the second fluidpath. The temperature of the heat absorbing fluid 116 at the end of thefourth portion 168 of the second fluid flow path may thus be greaterthan the temperature of the heat absorbing fluid 116 at the end of thethird portion 166 of the second fluid flow path, as well as beinggreater than the initial temperature of the heat absorbing fluid 116 atinlet 120.

The insulation layer 130 may be below and spaced apart from the secondporous light absorbing material layer 152. The insulation layer 130 maybe configured to provide a second flow channel 176 that forms part ofthe fourth portion 168 of the second fluid path. The fourth portion 168of the second fluid path may flow along the second flow channel 176,beneath the second porous light absorbing material layer 152, to theoutlet 122.

Further, with respect to the second fluid flow path, the solar thermalunit 100 may have one or more interstitial layers, such as secondinterstitial layer 170, between the second glazing layer 146 and thesecond porous light absorbing material layer 152. As illustrated, thesecond interstitial layer 170 may be a glazing or a different suitablematerial, and may be made of the same material or a different materialthat the second glazing layer 146 and/or may include one or morephotovoltaic (PV) panels. The second interstitial layer 170 may have atop surface 172 and a bottom surface 174. The top surface 172 of thesecond interstitial layer 170 is below and spaced apart from the innersurface 150 of the second glazing layer 146 and the bottom surface 174of the second interstitial layer 170 is above and spaced apart from thetop surface 154 of the second porous light absorbing material layer 152.

In examples where the solar thermal unit 100 includes a secondinterstitial layer 170, the second transition 162 may include a turn inthe second fluid path, around an end 196 of the second interstitiallayer 170. As illustrated in FIGS. 3 and 4, the second glazing layer 146has a length L₂, and the second interstitial layer 170 has a length thatis less than the length L₂ of the first glazing layer 146. The shorterlength of the second interstitial layer 170 creates a second gap 198between the end 196 of the first interstitial layer 146 and the sidewall 134 of the insulation layer 130. The turn of the second transition162 may redirect the heat absorbing fluid 116 over an angle that may beup to about 180°, including being between about 90° and about 180°. Thesecond interstitial layer 170 may have a width that is equal to thewidth W of the second glazing layer 146. In such an example, the firstportion 160 of the second fluid path extends from the inlet 120 alongthe inner surface 150 of the second glazing layer 146 between the innersurface 150 of the second glazing layer 146 and the top surface 172 ofthe second interstitial layer 170, and the second portion 164 of thesecond fluid path extends between the bottom surface 174 of the secondinterstitial layer 170 and the top surface 154 of the second porouslight absorbing material layer 152.

In examples where the solar thermal unit 100 includes a secondinterstitial layer 170, the heat absorbing fluid 116 may also extractheat from the second interstitial layer 170 as it flows along the secondfluid flow path. For example, as it travels along the first portion 160of the second fluid flow path, the heat absorbing fluid 116 may collectheat from along the inner surface 150 of the second glazing layer 146and from the top surface 172 of the second interstitial layer 170. Also,as it travels along the second portion 164 of the of the second fluidflow path, the heat absorbing fluid 116 may collect heat from along thebottom surface 174 of the second interstitial layer 170 and along thetop surface 154 of the porous light absorbing material layer 152. Asdiscussed above, the temperature gradient of the heat absorbing fluid116 may increase as the heat absorbing fluid flows along the secondfluid flow path from the inlet 120 to the outlet 122, and thetemperature of the heat absorbing fluid at the outlet 122 may be greaterthan the temperature of the heat absorbing fluid 116 at the inlet 120.

As shown in FIGS. 3 and 4, the first and second fluid flow paths mayeach be enclosed on the bottom and the sides by the insulation layer130, and on the top by the first glazing layer 102 or the second glazinglayer 146, respectively. The enclosed sections of the solar thermal unit100 may provide sealed flow chambers, such that the heat absorbing fluiddoes not leak out of the solar thermal unit 100 as it flows from theinlet 120 to the outlet 122. For example, a first sealed flow chamber178 may be provided that is bounded by the first glazing layer 102, thebottom 132 of the insulation 130, the side wall 134 of the insulation130, and a wall of the plenum 184. The first sealed chamber encloses thefirst fluid path. Similarly, a second sealed flow chamber 180 may beprovided that is bounded by the second glazing layer 146, the bottom 132of the insulation 130, the side wall 134 of the insulation 130, and awall of the plenum 184. The second sealed chamber encloses the secondfluid path.

The solar thermal unit 100 may also have a protective housing 182 thatsurrounds and encloses at least a portion of the fluid flow paths andthe components forming the fluid flow paths, including the insulationlayer 130.

As can be seen in FIGS. 3 and 4, the split-flow solar thermal unit 100may have a plenum 184 separating the first glazing layer 102 and firstporous light absorbing material layer 108 from the second glazing layer146 and the second porous light absorbing material layer 152. The plenum184 may have a plenum cover 186 and an upper plenum chamber 188 belowthe plenum cover 186. The inlet 120 may be located in the plenum 184.The inlet 120 may be configured to evenly divide and direct inflowingheat absorbing fluid between the first fluid path and the second fluidpath. The inlet may be further configured to cause the heat absorbingfluid to enter the upper plenum chamber 188.

In addition to creating thermal energy, some examples of solar thermalunits of the present technology may also create electrical energy. Insuch examples, the electrical energy may be created by a photovoltaicpanel (PV) 190 that includes one or more photovoltaic cells, which maycomprise at least a portion of the plenum cover 186. The heat absorbingfluid 116 that enters the upper plenum chamber 188 from the inlet 122may collect heat from the photovoltaic panel 190 before continuing alongthe first flow path or the second flow path. Because photovoltaic cellsoperate more efficiently when they are cooled, the heat absorbing fluidcollecting heat from the photovoltaic panel 190 may maintain or improvethe efficiency of the photovoltaic panel 190, as well as increasing theamount heat absorbed by the heat absorbing fluid. The rear side of thePV panel may be modified to promote flow interaction with the panel toenhance cooling of the panel. Additionally, the cell layout and wiringof the panel may be optimized to maximize the panels performanceconsidering temperature gradients across the panel.

One alternative example of a solar thermal unit 500 of the presenttechnology, having a single fluid flow path, is illustrated in FIG. 5.In at least some examples, the solar thermal unit 500 may be configuredsuch that the temperature gradient increases through the unit, along thefluid flow path from the inlet 520 to the outlet 522.

As shown, solar thermal unit 500 has a glazing layer 502 that has anouter surface 504 and an inner surface 506. The outer surface 504 of theglazing layer 502 may be exposed to ambient air. The solar thermal unit500 also has a porous light absorbing material layer 508, which is belowand spaced apart from the glazing layer 502. The porous light absorbingmaterial layer 508 has a top surface 510, a thickness 512, and a bottomsurface 514. A heat absorbing fluid 516 may flow through the solarthermal unit 500 along the fluid flow path from the inlet 520 to theoutlet 522.

When it enters the solar thermal unit 500 through inlet 520, the heatabsorbing fluid 516 may have an initial temperature, which may or maynot be equal to the temperature of the ambient air outside the solarthermal unit 500, depending upon the application. After entering thesolar thermal unit 500 through the inlet 520, at least part of the heatabsorbing fluid 516 may flow along a first portion 518 of the fluid flowpath, which extends from the inlet 520 along the inner surface 506 ofthe glazing layer 502. The heat absorbing fluid 516 may flow along theentire length of the inner surface 506 of the glazing layer 502 as itflows along the first portion 518 of the fluid flow path. Additionally,within the first portion 518 of the fluid flow path, the heat absorbingfluid 516 may be evenly distributed across the entire width of the innersurface 506 of the first glazing layer 502. As it travels along thefirst portion 518 of the fluid flow path, the heat absorbing fluid 116may collect heat from along the inner surface 506 of the first glazinglayer 502. The temperature of the heat absorbing fluid 516 at the end ofthe first portion 518 of the fluid flow path may thus be greater thanthe initial temperature of the heat absorbing fluid 516 at inlet 520.

After flowing through the first portion 518 of the fluid flow path, theheat absorbing fluid 516 may then flow through a transition 520 and thenalong a second portion 522 of the of the fluid flow path. The secondportion 522 of the fluid flow path extends along the top surface 510 ofthe porous light absorbing material layer 508. At least a portion of theheat absorbing fluid 516 may flow along the entire length of the topsurface 510 of the porous light absorbing material layer 508 as it flowsalong the second portion 522 of the of the fluid flow path.Additionally, within the second portion 522 of the of the fluid flowpath, the heat absorbing fluid 516 may be evenly distributed across theentire width of the top surface 510 of the porous light absorbingmaterial layer 508. As it travels along the second portion 522 of the ofthe fluid flow path, the heat absorbing fluid 516 may collect heat fromalong the top surface 510 of the porous light absorbing material layer508. The temperature of the heat absorbing fluid 516 at the end of thesecond portion 522 of the fluid flow path may thus be greater than thetemperature of the heat absorbing fluid 516 at the end of the firstportion 518 of the fluid flow path, as well as being greater than theinitial temperature of the heat absorbing fluid 516 at inlet 520.

After flowing through the second portion 522 of the of the fluid flowpath, the heat absorbing fluid 516 may then flow along a third portion524 of the first fluid path, through the thickness 512 of the porouslight absorbing material layer 508. The heat absorbing fluid 516 maycollect heat from within the porous light absorbing material layer 508as if flows along the third portion 524 of the fluid path. Thetemperature of the heat absorbing fluid 516 at the end of the thirdportion 524 of the fluid flow path may thus be greater than thetemperature of the heat absorbing fluid 516 at the end of the secondportion 522 of the fluid flow path, as well as being greater than theinitial temperature of the heat absorbing fluid 516 at inlet 520.

After flowing through the third portion 524 of the of the fluid flowpath, the heat absorbing fluid 516 may then flow along a fourth portion526 of the fluid path, along the bottom surface 514 porous lightabsorbing material layer 508 to the outlet 522, where the heat absorbingfluid may exit the solar thermal unit 500. The heat absorbing fluid 516may collect heat from the bottom surface 514 porous light absorbingmaterial layer 508, as well as from any other components, such as theinsulation layer 534, that it contacts as if flows along the fourthportion 526 of the fluid path. The temperature of the heat absorbingfluid 516 at the end of the fourth portion 526 of the fluid flow pathmay thus be greater than the temperature of the heat absorbing fluid 516at the end of the third portion 524 of the fluid flow path, as well asbeing greater than the initial temperature of the heat absorbing fluid516 at inlet 520.

The solar thermal unit 500 may also have an insulation layer 534, whichmay have a bottom 536 and a side wall 538. The insulation layer 534 maybe below and spaced apart from the porous light absorbing material layer508. The insulation layer 534 may be configured to provide a first flowchannel 540 that forms part of the fourth portion 526 of the fluid path.The fourth portion 526 of the fluid path may flow along the first flowchannel 540, beneath the porous light absorbing material layer 508, tothe outlet 522.

Further, the solar thermal unit 500 may have at least one interstitiallayer, such as interstitial layer 528, between the glazing layer 502 andthe porous light absorbing material layer 508. The interstitial layer528 may be a glazing or a different suitable material, and may be madeof the same material or a different material that the glazing layer 202.The interstitial layer 528 may have a top surface 530 and a bottomsurface 532. The top surface 530 of the interstitial layer 528 is belowand spaced apart from the inner surface 506 of the glazing layer 502 andthe bottom surface 532 of the interstitial layer 528 is above and spacedapart from the top surface 510 of the porous light absorbing materiallayer 508.

In examples where the solar thermal unit 500 includes an interstitiallayer 528, the transition 520 may include a turn in the first fluidpath, around an end 542 of the interstitial layer 528. As illustrated inFIG. 5, the glazing layer 502 has a length and the interstitial layer528 has a length that is less than the length of the glazing layer 502.The shorter length of the interstitial layer 528 creates a first gap 544between the end 542 of the interstitial layer 528 and the side wall 538of the insulation layer 534. The turn of the transition 520 may redirectthe heat absorbing fluid 516 over an angle that may be up to about 180°,including being between about 90° and about 180°. The interstitial layer528 may have a width that is equal to the width of the glazing layer502. In such an example, the first portion 518 of the fluid path extendsfrom the inlet 520 along the inner surface 504 of the glazing layer 502between the inner surface 504 of the glazing layer 502 and the topsurface 530 of the interstitial layer 528, and the second portion 522 ofthe fluid path extends between the bottom surface 532 of theinterstitial layer 528 and the top surface 510 of the porous lightabsorbing material layer 508. The second portion 522 of the fluid pathmay be in contact with the bottom surface 532 of the interstitial layer528, and may thereby collect heat from the first interstitial layer 528.

In examples where the solar thermal unit 500 includes a firstinterstitial layer 528, the heat absorbing fluid may also extract heatfrom the interstitial layer 528 as it flows along the fluid flow path.For example, as the heat absorbing fluid 516 travels along the firstportion 518 of the fluid flow path, the heat absorbing fluid 516 maycollect heat from along the inner surface 506 of the first glazing layer502 and from the top surface 530 of the first interstitial layer 528.Also, as it travels along the second portion 522 of the of the fluidflow path, the heat absorbing fluid 516 may collect heat from along thebottom surface 532 of the first interstitial layer 528 and along the topsurface 510 of the porous light absorbing material layer 508. Asdiscussed above, the temperature gradient of the heat absorbing fluid516 may increase as the heat absorbing fluid flows along the first fluidflow path from the inlet 520 to the outlet 522, and the temperature ofthe heat absorbing fluid at the outlet 522 may be greater than thetemperature of the heat absorbing fluid 516 at the inlet 520.

Additional alternative examples of solar thermal units 600 and 700 ofthe present technology are shown in FIGS. 6 and 7, respectively.

As shown in FIG. 6, solar thermal unit 600 has two fluid flow pathssimilar to those illustrated and discussed above with respect to FIGS.1-4. Instead of having a second glazing layer, however, solar thermalunit 600 has only a first glazing layer 602, which has a length L andextends across the top of both fluid flow paths. As shown, solar thermalunit 600 has a first glazing layer having an outer surface 604 and aninner surface 606. The outer surface 604 of the first glazing layer 602may be exposed to ambient air. Solar thermal unit 600 also has a firstporous light absorbing material layer 608 below and spaced apart fromthe first glazing layer 602 on a first side of the solar thermal unit600. The first porous light absorbing material layer 608 has a topsurface 610, a thickness 612, and a bottom surface 614. Solar thermalunit 600 also has a second porous light absorbing material layer 616below and spaced apart from the first glazing layer 602 on a second sideof the solar thermal unit 600, opposite the first side of the solarthermal unit 600. The second porous light absorbing material layer 616has a top surface 618, a thickness 620, and a bottom surface 622. Solarthermal unit 600 further has a first interstitial layer 638 and a secondinterstitial layer 640.

Heat absorbing fluid 624 enters the solar thermal unit 600 through aninlet 626 in the plenum 628, which separates the first porous lightabsorbing material layer 608 from the second porous light absorbingmaterial layer 616. A first portion, which may be half, of the heatabsorbing fluid 624 flows along the first fluid flow path 630 from inlet626 along the inner surface 606 of the first glazing layer and thenthrough the thickness of the first porous light absorbing material layer608 to the outlet 634. A second portion, which may also be half, of theheat absorbing fluid 624 flows along the second fluid flow path 632 fromthe inlet 626 along the inner surface 606 of the first glazing layer andthen through the thickness of the second porous light absorbing materiallayer 616 to the outlet 634.

The flow of the heat absorbing fluid 624 through solar thermal unit 600is the same as, or substantially the same as, the flow along the fluidpaths of solar thermal unit 100, described above. However, in solarthermal unit 600, the plenum cover 636 is below and spaced apart fromthe first glazing layer 602, which may be even with the first and secondinterstitial layers 638 and 640. As shown, the plenum cover 636 mayinclude one or more photovoltaic cells. The inlet 626 may be configuredto evenly divide and direct inflowing heat absorbing fluid 624 betweenthe first fluid path and the second fluid path. The inlet 626 may befurther configured to cause the heat absorbing fluid to enter the plenumbelow the plenum cover 636, and then flow over the plenum cover 636 asit is divided along each flow path. Such a configuration may allow theheat absorbing fluid 624 to collect heat from the beneath and above theplenum cover 636, and any of the one or more PV panels that are part ofthe plenum cover 636.

As shown in FIG. 7, solar thermal unit 700 is similar in structure andflow to solar thermal unit 600. Solar thermal unit 700 has a firstglazing layer 702 having a length L and extends across the top of bothfluid flow paths. In this example, a first end of each of the firstinterstitial layer 704 and the second interstitial layer 706 may act asthe plenum cover. Moreover, each of the first interstitial layer 704 andthe second interstitial layer 706 may include one or more PV panels. Inthis example, the area of PV panel that can be included is greater thanthe area of PV panel in the other illustrated examples. The heatabsorbing fluid 708 can enter the solar thermal unit 700 through inlet710, below the portion of each of the first and second interstitiallayers 704 and 706 acting as the plenum cover. The heat absorbing fluidmay then divide and flow along each of the fluid flow paths, gatheringheat from the top of the PV panels of the first interstitial layer 704and the second interstitial layer 706, and then from the bottom of thePV panels of the first interstitial layer 704 and the secondinterstitial layer 706, before flowing through the first and secondporous light absorbing material layers 712 and 714 to the outlet 716. Insolar thermal unit 700, it may be advantageous for the thickness of thefirst and second interstitial layers 704 and 706 acting as the plenumcover to be reduced as much as practical, and for the thickness of thefirst and second porous light absorbing material layers 712 and 714 tobe increased.

FIGS. 12-13 illustrate a fifth example of a solar thermal unit 1000 ofthe present technology. The solar thermal unit 1000 has a split-flowdesign having two fluid flow paths, a first fluid flow path on the rightand a second fluid flow path on the left. It should be understood thatthe second fluid flow path may have the same set of components as thefirst fluid flow path, and may be a mirror image of the first fluid flowpath. The flow paths of this design are altered as compared to the flowpaths of solar thermal unit 100, with the heat absorbing fluid flowingfirst to the outer edges of the unit and then flowing along the bottomsurface of the first glazing layer towards the center of the unit.

A shown, solar thermal unit 1000 includes a first glazing layer 1002that extends across both the first fluid flow path 2000 and the secondfluid flow path 2002. The first glazing layer 1002 has an outer surface1004 and an inner surface 1006. The outer surface 1004 of the firstglazing layer 1002 may be exposed to ambient air.

The first fluid flow path 2000 of the solar thermal unit 1000 has afirst porous light absorbing material layer 1008, which is below andspaced apart from the first glazing layer 1002. The first porous lightabsorbing material layer 1008 has a top surface 1010, a thickness 1012,and a bottom surface 1014.

The first fluid flow path 2000 of the solar thermal unit 1000 also has afirst interstitial layer 1016 between the first glazing layer 1002 andthe first porous light absorbing material layer 1008, the firstinterstitial layer 1016 has a top surface 1018 and a bottom surface1020. The top surface 1018 of the first interstitial layer 1016 is belowand spaced apart from the inner surface 1006 of the first glazing layer1002, and the bottom surface 1020 of the first interstitial layer 1016is above and spaced apart from the top surface 1010 of the first porouslight absorbing material layer 1008. The first interstitial layer mayinclude a PV panel 1022 and a second glazing layer 2024.

The second fluid flow path 2002 of the solar thermal unit 1000 has asecond porous light absorbing material layer 1044, which is below andspaced apart from the first glazing layer 1002. The second porous lightabsorbing material layer 1044 has a top surface 1046, a thickness 1048,and a bottom surface 1050.

The second fluid flow path 2002 of the solar thermal unit 1000 also hasa second interstitial layer 1052 between the first glazing layer 1002and the second porous light absorbing material layer 1044, the secondinterstitial layer 1052 has a top surface 1054 and a bottom surface1056. The top surface 1054 of the second interstitial layer 1052 isbelow and spaced apart from the inner surface 1006 of the first glazinglayer 1002, and the bottom surface 1056 of the second interstitial layer1052 is above and spaced apart from the top surface 1046 of the secondporous light absorbing material layer 1044. The second interstitiallayer may include a PV panel 1058 and a third glazing layer 1060.Additionally, the first interstitial layer 1016 and the secondinterstitial layer 1052 may be spaced apart to provide a firsttransition 1062 through which the heat absorbing fluid of the first andsecond flow paths can pass.

The solar thermal unit 1000 also includes an inlet plenum 1026, whichhas an inner surface 1028. The inlet plenum has an inlet 1030, throughwhich the heat absorbing fluid 1034 enters the solar thermal unit 1000,and an outlet 1032, through which the heat absorbing fluid 1034 exitsthe solar thermal unit 1000. The solar thermal unit, including the inlet1030, may be configured to divide the heat absorbing fluid evenly, sothat a first half of the heat absorbing fluid flows along the firstfluid flow path 2000 and a second half of the heat absorbing fluid flowsalong the second fluid flow path 2002. Balancing the flow by providingeven distribution between the flow paths can reduce or eliminate hotspots that can occur on the first glazing layer, which can reduce heatloss through the first glazing layer and improve efficiency.

The solar thermal unit 1000 further includes an insulation layer 1036between the inlet plenum 1026 and the first porous light absorbingmaterial layer 1008. The insulation layer has a top surface 1038 and abottom surface 1040.

The solar thermal unit 1000 may include a protective housing 1042, whichmay surrounds and encloses at least a portion of the fluid flow pathsand the components forming the fluid flow paths, including the inletplenum 1026.

The heat absorbing fluid 1034 enters the solar thermal unit 1000 throughthe inlet 1030, and is divided to flow along the first fluid flow pathand the second fluid flow path.

As shown in FIG. 13, the first fluid flow path 2000 flows from the inlet1030, to the right, between the inner surface 1028 of the inlet plenum1026 and the bottom surface 1040 of the insulation layer 1036. Next, thefirst fluid flow path 2000 flows along the inner surface 1006 of thefirst glazing layer 1002. The heat absorbing fluid absorbs heat fromalong the inner surface 1006 of the first glazing layer 1002, as well asfrom along the top surface 1018 of the first interstitial layer 1016,including any PV panel that is a component thereof. Accordingly, thetemperature of the heat absorbing fluid after flowing along the innersurface 1006 of the first glazing layer 1002 is greater than thetemperature of the heat absorbing fluid at the inlet 1030.

Next, the first fluid flow path 2000 flows through a first transition1062, which is shown as being the space between the spaced apart firstinterstitial layer 1016 and the second interstitial layer 1052. At andwithin the first transition 1062, heat absorbing fluid of the first flowpath may intermingle with heat absorbing fluid of the second flow path,before the flow splits to continue along the two fluid flow paths. Thefirst transition 1062 may be configured to join the first and secondflow paths, and then split the first and second flow paths so that theheat absorbing fluid is divided evenly between the two fluid flow paths.

Next, the first fluid flow path 2000 flows along the bottom surface ofthe first interstitial layer and the top surface of the first porouslight absorbing material layer 1008, and the and then through thethickness 1012 of the first porous light absorbing material layer 1008to the outlet 1032. The heat absorbing fluid 1034 flowing along thefirst fluid flow path 2000 absorbs heat from along the bottom surface ofthe first interstitial layer, including any PV panel that is a componentthereof, and the top surface of the first porous light absorbingmaterial layer 1008. The heat absorbing fluid flowing along the firstfluid flow path 2000 also absorbs heat from within the thickness of thefirst porous light absorbing material layer 1008. Accordingly, thetemperature of the heat absorbing fluid after flowing through the firstporous light absorbing material layer 1008 may be greater than thetemperature of the heat absorbing fluid 1034 at the inlet 1030.

The second fluid flow path 2002 flows from the inlet 1030, to the left,between the inner surface 1028 of the inlet plenum 1026 and the bottomsurface 1040 of the insulation layer 1036. Next, the second fluid flowpath 2002 flows along the inner surface 1006 of the first glazing layer1002. The heat absorbing fluid absorbs heat from along the inner surface1006 of the first glazing layer 1002, as well as from along the topsurface 1054 of the second interstitial layer 1052. Accordingly, thetemperature of the heat absorbing fluid after flowing along the innersurface 1006 of the first glazing layer 1002 is greater than thetemperature of the heat absorbing fluid at the inlet 1030.

Next, the second fluid flow path 2002 flows through the first transition1062, between the spaced apart first interstitial layer 1016 and thesecond interstitial layer 1052. At and within the first transition 1062,heat absorbing fluid of the second flow path may intermingle with heatabsorbing fluid of the first flow path, before the flow splits tocontinue along the two fluid flow paths.

Next, the second fluid flow path 2002 flows along the bottom surface1056 of the second interstitial layer 1052 and the top surface 1046 ofthe second porous light absorbing material layer 1044, and the and thenthrough the thickness 1048 of the first porous light absorbing materiallayer 1044 to the outlet 1032. The heat absorbing fluid 1034 flowingalong the second fluid flow path 2002 absorbs heat from along the bottomsurface 1056 of the second interstitial layer 1052 and the top surface1046 of the first porous light absorbing material layer 1044. The heatabsorbing fluid flowing along the second fluid flow path 2002 alsoabsorbs heat from within the thickness 1048 of the second porous lightabsorbing material layer 1044. Accordingly, the temperature of the heatabsorbing fluid after flowing through the second porous light absorbingmaterial layer 1044 may be greater than the temperature of the heatabsorbing fluid 1034 at the inlet 1030.

As discussed above, the temperature gradient of the heat absorbing fluid1034 may increase as the heat absorbing fluid flows along either thefirst fluid flow path 2000 or the second fluid flow path, from the inlet1030 to the outlet 1032, and the temperature of the heat absorbing fluidat the outlet 1032 may be greater than the temperature of the heatabsorbing fluid 1034 at the inlet 1030.

Materials

The specific examples of solar thermal units described with respect toFIGS. 1-5 above use air, specifically ambient air, as the heat absorbingfluid. Ambient air normally contains a mixture of gaseous components,including oxygen and nitrogen. In alternative examples, other heatabsorbing fluids could be used, which may be in either gaseous or liquidform. Some non-limiting examples of other heat absorbing fluids includewater, helium, argon, water, steam, and mixtures of these componentswith each other or with other components.

Glazing layers for use in solar thermal units of the present technologyare transparent layers configured to allow sunlight to penetrate intothe solar thermal unit through the glazing layer and into the porouslight absorbing layer. A glazing layer may be made of any suitablematerial, including for example: glass, acrylic, FEP, a polymer, apolycrystalline material, derivatives of any of the foregoing, orcombinations of any of the foregoing. When glass is used, the glass maybe soda lime, iron free or low iron glass. The infrared (IR) opacity ofthe glazing layer is not as critical in solar thermal units of thepresent technology, where the air, or other heat absorbing fluid, flowsthrough the solar thermal unit, as compared to typical solar thermalunits having stagnant air. Glazing layers may also be surface treated orcoated to promote transmission and/or reduce radiative losses throughthe glazing.

Porous heat absorbing layers for use in solar thermal units of thepresent technology may be made of any suitable material that absorbsheat and configured for flow-through of the heat absorbing fluid,including for example: metals, mineral wool, and thermally stablepolymers. In some examples, the porous heat absorbing layer may be madeof a black material, or have a black coating or selective film appliedto the top surface thereof. A porous heat absorbing layer of the presenttechnology may include a plurality of sub-layers, where each sub-layercaptures a percentage of the heat absorbed by the overall porous heatabsorbing layer. The view factor of each sub-layer of the porous heatabsorbing layer directly affects the percentage of the heat captured byeach layer through the thickness from the top surface to the bottomsurface. It may be desirable to configure the porous heat absorbinglayer to have an optimized thermal mass, which may be a small aspracticable, in order to reduce the time period needed for the porousheat absorbing layer to reach a desired temperature. It may also bedesirable for the porous heat absorbing layer to be configured such thatit has a non-linear temperature profile, such as illustrated in FIG. 8,where the temperature at any given time during operation of the solarthermal unit is a lower at the top surface, and in the initial layers,and increases in the lower layers to a maximum near or at the bottomsurface.

Insulation layers for use in solar thermal units of the presenttechnology may be made of any suitable material that functions to reducethe loss of radiated heat from the solar thermal unit.

Housing for use in solar thermal units of the present technology may bemade of any suitable material, including for example galvanized steel.Heat Transfer and Absorption

A computational simulation tool was developed to solve the completesystem of equations describing heat transfer in the solar thermal unit.The equations are solved simultaneously for each component in the systemin an iterative fashion until the solution has converged. A componentcan be a section of material in the solar unit, or a section of thecarrier fluid.

Generally, heat transfer for the solar insolation is equal to theabsorptivity of any given component times the incident solar insolation.Heat transfer communication with the component may be with anothercomponent, the carrier fluid, or ambient surfaces and/or sky. Duringoperation of solar thermal units of the present technology, such assolar thermal unit 100, heat may transfer to the heat absorbing fluid infour stages: (1) forced internal convection from the glazing layer andany interstitial layer in the first portion of the fluid path 118, 160,518, (2) forced internal convection from the interstitial layer and thetop surface of the porous heat absorbing layer in the second portion onthe fluid path 140, 164, 522, (3) porous flow convection from the porousheat absorbing layer in the third portion on the fluid path 142, 166,524, and (4) forced internal convection from the bottom surface of theporous heat absorbing layer and the insulation in the fourth portion onthe fluid path 144, 168, 526.

In the first, second, and fourth portions of the fluid path, heattransfer to the heat absorbing fluid under forced convection may begoverned by the equation for forced convection between two flat plates:

$\begin{matrix}{Q_{{Flat}\mspace{14mu}{Plate}} = {{\frac{{Nu}_{{Flat}\mspace{14mu}{Plate}}*k}{th}A*\left( {T_{F} - T_{M}} \right)}:}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

where Q is the transferred power (W). Nu is the non-dimensional Nusseltnumber (M8 for parallel plates). The value of k is the thermalconductivity of the heat absorbing fluid (W/(mK)). A is the area of eachplate (m²) through which the flow travels, such as the first glazinglayer 102 and the first interstitial layer 126, the second glazing layer146 and the second interstitial layer 170, the glazing layer 502 and theinterstitial layer 528, or the bottom surface of the porous heatabsorbing layers and the bottom of the insulation layer. TF is thetemperature of the heat absorbing fluid (C). TM is the temperature ofthe material. The denominator th is the thickness between the twoplates.

In the third portion on the fluid path 142, 166, 524, heat transfer tothe heat absorbing fluid may be governed by:

$\begin{matrix}{Q_{Porous} = {{\frac{{Nu}_{Porous}*k}{th}A_{Eff}*\left( {T_{F} - T_{M}} \right)}:}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

where Nu_(Porous) is on the order of M 100 for porous materials andA_(Eff) is the effective surface area of the material (typically afactor of several hundred times the volume of the material), and th isthe thickness of the absorber.

Heat transfer between individual solar thermal components can occur byeither convection or radiation. Radiation may be governed by:

$\begin{matrix}{Q_{rad} = {\frac{\sigma\left( {T_{1}^{4} - T_{2}^{4}} \right)}{\frac{1}{\in 1} + \frac{1}{\in 2}}:}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

where Qrad is the radiated power, T₁ and T₂ are the temperatures of thetwo communicating surfaces, a is the Stefan-Boltzmann constant, and ∈1and ∈2 are the emissitivities of the two surfaces. The equation caninclude a View Factor multiplier to account for a porous materialtransmitting some radiation through the pores, and thus a componentmight “see through” that component to pick up additional radiation fromanother component.

Heat from the solar flux in each component may be governed by:

Q _(Flux)=α*F*A   Equation 4:

where α is the absorptivity of the material and F is the solar fluxincident on that material (W/m2, taking into account that innercomponents see a flux equal to the total flux times the transmissivityof the components above).

In determining how the system functions, radiative and convective heatloss of a solar thermal unit of the present technology may also be takeninto account. Radiative heat transfer to ambient may use the sameequation as radiative transfer between components. Convective heattransfer may be governed by:

$\begin{matrix}{Q_{{Amb}.{Conv}.} = {{\left( {5.7 + {3.8*{Wind}_{Velocity}}} \right)*A*\left( {T_{Surface} - T_{Ambient}} \right)}:}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

where Q_(Amb.Conv.) is the convective heat loss, Wind_(velocity) is thevelocity of the wind in the immediate vicinity of the solar thermalunit, T_(surface) is the temperature of the relevant surface of thesolar thermal unit, and T_(ambient) is the ambient temperature in theimmediate vicinity of the solar thermal unit.

The iterative solution begins by assuming that each component begins ata temperature equal to the ambient temperature. The temperature is thenadvanced in time as follows:

$\begin{matrix}{T_{new} = {T_{old} + {\frac{\Delta\; t}{mCp}{\sum\limits_{All}{Q_{component}:}}}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

where T is the temperature of the component, t is the time, m is themass of the component, C_(p) is the specific heat of the components, andQ_(component) is the heat transfer for each individual component. Thetime step is selected such the change in T is small compared to themagnitude of T. T_(old) is then replaced with T_(new) and thetemperature is advanced another step forward in time. This process isrepeated until the change in temperature for each step falls below aspecified “stop” criteria, at which point the system of equations isconsidered to have converged and the final set of temperatures is thesolution.

Efficiency of the system may be defined as the thermal energytransferred to the carrier fluid divided by the total solar insolationon the system as follows:

$\begin{matrix}{{Eff} = {\frac{\overset{.}{m}{{Cp}\left( {T_{fluid\_ out} - T_{fluid\_ in}} \right)}}{{Flux}*{Area}}:}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

where m is the mass flow rate of the carrier fluid. The remaining energythat is absorbed from the solar flux but not transmitted to the carrierfluid is communicated back to the environment by radiative andconvective heat transfer from an external surface (typically the toppane of glass and the outside of the insulation) to ambient.

The above system of equations describes the heat transfer in nearly anysolar thermal unit design. The examples described herein may producehigher efficiencies than traditional solar thermal units (such as a flatplate unit) for two reasons. One is that the convective heat transferbetween the porous material and the carrier fluid may be significantlyfaster than that in a flat plate collection. The second is that the flowpath in the porous design may be routed in such a way as to carry heataway from the top pane of glass (where most losses to ambient occur) andto ensure that the hotter components in the solar thermal are in moreinternal locations where the heat escapes back to ambient more slowly.Fluid Flow and Pressure Drop

The efficiency and power usage of a solar thermal unit of the presenttechnology may be affected by the flow of the heat absorbing fluidthrough each fluid path and the pressure drop across any fluid pathwithin the unit.

Minimizing the pressure drop may reduce the amount of power required topump the heat absorbing fluid through the system at a desired flow rate.Using a split-flow design, such as the example illustrated in FIGS. 1-4may balance the pressure drop across the unit, and cut the pressure dropin half as compared to solar thermal units having only a single fluidpath.

Uniformity of the air flow may be controlled by careful tolerance of thespace between components of the thermal solar unit to control thepressure drop. There are three equations that may govern the flow alongthe fluid paths described herein. Design of the system may be governedby the following equations:

Couette Flow (steady flow between parallel plates), for setting thedistance between the glazing:

${\Delta\; P} = \frac{12\mu\;{LQ}}{h^{3}w}$

A modified Couette Flow (accounting for flow exiting or entering theporous heat absorbing layer) for the distances above and below theporous heat absorbing layer, porous heat absorbing layer to glazing orinterstitial layer, and porous heat absorbing layer to bottom ofinsulation layer, respectively.

${\Delta\; P} = {\frac{6\mu}{w}\frac{QL}{\left( {2h_{i}^{2}h_{o}} \right)}}$

Darcy Flow through the porous heat absorbing layer, to determine thedesired thickness of the porous heat absorbing layer.

${\Delta\; P} = \frac{Q\;\mu\; t}{kLw}$

Netwons second law for fluid momentum may be used to determine thepressure drop required to turn flow 90 degrees at the inlet, outlet, andthe transition (must be doubled because the flow turn 180 degrees) alonga given fluid path.

${\Delta\; P} = {\frac{1}{2}\rho\; v^{2}}$

In these equations, ΔP is the pressure drop (Pa), μ is the viscosity ofthe fluid (Pa·s), L is the length of the section (m), Q is the flow rate(m3/s), h is the gap thickness (m, initial and final if it varies), w isthe width of the section (m), t is the thickness of the porous region(m), k is the diffusivity of the porous heat absorbing layer (m2/s), ρis the density of the fluid (kg/m{circumflex over ( )}3), v is thevelocity of the fluid (m/s) and A is the area through which the fluid ispassing.

The area of the transition must be at least as large of an area as thecross sectional area between the glazing and the interstitial layer inorder to prevent large pressure drops at the transition.

EXAMPLE 1

A solar thermal unit of the present technology having the flow describedabove with respect to solar thermal unit 100 and an insulated plenumcover was made using the following materials and parameters.

The system comprised of a split-flow design where the each of theglazing and interstitial layers were made of iron free glass. Theinsulation was constructed of polyisocyanurate insulation (R-Value 6).The housing was 0.6 mm thick galvanized steel. Each of the porous heatabsorbing layers was made with 1″ thick mineral wool painted black tominimize reflective losses. The plenum cover was polyisocyanurateinsulation. Total absorbing area was approximately two square meters.The spacing between the glazing and the interstitial layer for each flowpath was set at 1/8^(th) inch. Each interstitial layer had dimensions of36.5″ long and 47.5″ wide, while each glazing layer was 38.5″ ling and47.5″ wide. The glazing layers were each supported by approximately 0.5″on each side, and the gap of each transition was about 1.0″. Thedistance between each interstitial layer and each porous heat absorbinglayer, and also between each porous heat absorbing layer and the bottomof the insulation, was about 1.25″. The solar thermal unit wascalibrated by providing forced air with a blower through a meter atknown volumetric flow rates. The resulting pressure across the panes ofglass was measured. This pressure was then matched with flow providedfrom a DC fan.

The solar thermal unit was tested over a period of about 5 hours on aday that started out sunny and became cloudy for the last hour. The flowrate, measured in cubic feet per minute (CFM), was varied on an hourlybasis. Specifically, the flow rate during the first hour was set to 40CFM and the flow rate during the second hour was set to 50 CFM Theambient temperature, which was also the temperature at the inlet, wasmeasured each hour. The results are illustrated in FIG. 9. Theefficiency of the system was determined based on the insolation overtime, and is set forth in Table 1 below.

TABLE 1 Flow T_(in) = (CFM) T_(amb) (° C.) Efficiency 40 17.5 45% 5018.6 49%

EXAMPLE 2

A solar thermal unit of the present technology having a PV panelincorporated into the plenum cover was made using the followingmaterials and parameters.

The system comprised of a split flow design where each of the glazingand interstitial layers was made of iron free glass. The insulation wasconstructed of polyisocyanurate insulation (R-Value 6). The housing was0.6 mm thick galvanized steel. Each of the porous heat absorbing layerswas made with 1″ thick mineral wool painted black to minimize reflectivelosses. The plenum cover included a PV panel. Dimensions of the PV panelwere 46.5″ wide and 17.4″ long. The spacing between each glazing layerand each interstitial layer was set at 118^(th) inch. Each interstitiallayer had dimensions of 36.5″ long and 47.5″ wide, while each glazinglayer was 38.5″ ling and 47.5″ wide. The glazing layers were eachsupported by approximately 0.5″ on each side, and the gap of eachtransition was about 1.0″. Total absorbing area (not including the areaof the PV panel) was approximately two square meters. The distancebetween each interstitial layer and each porous heat absorbing layer,and also between each porous heat absorbing layer and the bottom of theinsulation, was about 1.25″. The solar thermal unit was calibrated byproviding forced air with a blower through a meter at known volumetricflow rates. The resulting pressure across the panes of glass wasmeasured. This pressure was then matched with flow provided from a DCfan.

The solar thermal unit was mounted on a scissor-jack system, whichallowed the orientation of the solar thermal unit to be altered byrotation through a range of angles, from 0° to 45°. The ability toadjust the angle at which the solar thermal unit is advantageous, suchas when using the solar thermal unit during different times of the yearor in geographic areas of different latitude, allowing the solar thermalunit to be oriented as directly towards the sun as possible.

EXAMPLE 3

FIG. 14 and Table 2 below provide the results of efficiencydeterminations for a solar thermal units of the present technologyhaving the design of solar thermal unit 100 (Design 1) versus thereverse flow design of solar thermal unit 1000 (Design 2). In FIG. 14,the graph on the left shows the efficiency at a flow rate of 40 cfm. Thegraph on the right shows the efficiency at a flow rate of 50 cfm. Thex-axis for each graph is the temperature at the inlet, expressed in thenumber of degrees above ambient.

Efficiency was calculated using this equation:

${Efficiency} = \frac{{{Thermal}\mspace{14mu}{Power}} + {{Electrical}\mspace{14mu}{Power}}}{{Insolation}*{Panel}\mspace{14mu}{Area}}$

where thermal power is calculated using the numerator of the equationfrom paragraph 89 and electrical power produced by the PV panel iscalculated using the following equation:

Electrical Power−=Volts*Amps

Additionally, the insolation was measured directly from a pyranometerplaced on the panel during testing and the panel area is equal to 2.92m².

As can be seen in FIG. 14 and Table 2, the efficiency for each of thedesigns at either flow rate is the highest when the temperature at theinlet equals the ambient temperature (0 on the x-axis). As can also beseen, the reverse flow design provided higher efficiency at both flowrates across the tested temperature range.

TABLE 2 Design Efficiency at Various Operating Conditions Tinlet- FlowTambient Design (CFM) (deg. C.) Efficiency 1 40  0 45% 1 40 15 36% 1 50 0 49% 1 50 15 41% 2 40  0 49% 2 40 15 42% 2 50  0 52% 2 50 15 43%

Applications

Solar thermal units of the present technology may be used in a number ofapplications, including residential, commercial, and industrialapplications. For example, solar thermal units of the present technologymay be used for residential heating of air and/or water, and may bemounted on the roof of a residential building or on the ground near aresidential building. As another example, solar thermal units of thepresent technology may be used in any commercial or industrialapplication where heating of air or any other heat absorbing fluid isdesired. In at least one example, a solar thermal unit of the presenttechnology may be used as the thermal unit in a system for generatingliquid water from air, such as the system described in U.S. ProvisionalPatent Application Ser. No. 62/145995, filed on Apr. 10, 2015, which isincorporated herein by reference in its entirety.

One example where a solar thermal unit of the present technology may beused as the thermal unit in a system for generating liquid water fromair is illustrated in FIG. 10. The system 800 of FIG. 10 may beconfigured to function responsive to diurnal variations. For example, asdescribed in more detail below, system 800 may be configured to controlone or more operational parameters (e.g., control and/or controlledvariables) based on one or more diurnal variations (e.g., variations inambient air temperature, ambient air relative humidity, solarinsolation, and/or the like).

System 800 may comprise a desiccant unit 802. Desiccant unit 802 maycomprise a desiccant (e.g., sorption medium) 804, where the desiccantunit 802 (e.g., or a portion thereof) may be selectively (e.g., and/oralternatively) movable between an adsorption zone 806, in which thedesiccant is in fluid communication with a process air pathway (e.g., aprocess airflow path) 810 and a desorption zone 808, in which thedesiccant is in fluid communication with a (e.g., closed-loop)regeneration fluid pathway (e.g., a regeneration fluid path) 812. Insome embodiments, the adsorption and desorption zones may be defined bya housing (e.g., 814) of the desiccant unit 802.

Desiccant unit 802 may operate in a continuous, or non-batch, fashion,such that desiccant unit 802 is configured to absorb water and desorbwater substantially simultaneously or simultaneously. For example,system 800 may be configured such that a first portion of desiccant unit804 can be disposed within adsorption zone 806 (e.g., such that thefirst portion can capture water from process air in process air pathway810), with a second portion of the desiccant simultaneously disposedwithin the desorption zone (e.g., such that the second portion candesorb water into regeneration fluid in regeneration fluid pathway 812).Regeneration fluids suitable for use in some embodiments of the presentsystems may include, but are not limited to, air (e.g., including anysuitable amount of water vapor), super-saturated or high relativehumidity gas (e.g., 90-100% relative humidity), glycols, ionic liquids,and/or the like.

Desiccant unit 802 may comprise a hygroscopic material (e.g., desiccantor sorption medium 804) configured to continuously alternate between aprocess air pathway 810 and a regeneration fluid pathway 812. In someembodiments, that the desiccant or sorption medium may be capable ofquickly desorbing water back into low relative humidity air (e.g., toregenerate the desiccant). Therefore, in some embodiments, theperformance of the desiccant or sorption medium may be driven by anability to quickly cycle through an absorption state and a desorptionstate.

Desiccant 804 may comprise any suitable medium in any suitableconfiguration (e.g., such that the desiccant or sorption medium iscapable of adsorption and desorption of water). In some embodiments, thedesiccant or sorption medium may be capable of sorption at a firsttemperature and/or pressure and desorption at a second temperatureand/or pressure. Suitable desiccants or sorption mediums may compriseliquids, solids, and/or combinations thereof. In some embodiments,desiccants or sorption mediums may comprise any suitable porous solidimpregnated with hygroscopic materials. For example, desiccant unit 804may comprise silica, silica gel, alumina, alumina gel, montmorilloniteclay, zeolites, molecular sieves, activated carbon, metal oxides,lithium salts, calcium salts, potassium salts, sodium salts, magnesiumsalts, phosphoric salts, organic salts, metal salts, glycerin, glycols,hydrophilic polymers, polyols, polypropylene fibers, cellulosic fibers,derivatives thereof, and combinations of thereof. In some embodiments,the desiccant or sorption medium may be selected and/or configured toavoid sorption of certain molecules (e.g., molecules that may bepoisonous when consumed by a human).

In some embodiments, desiccant particles may be packed in a shallow bedto maximize a surface area for interaction with air or fluid withinadsorption zone 806 and desorption zone 808. In some embodiments, thedesiccant particles may be agglomerated via a binder. In someembodiments, the desiccant particles may be dyed black (e.g., to improveabsorption of thermal radiation). In some embodiments, the desiccantparticles may be mixed and/or combined with thermal radiation absorbingmaterials.

System 800 may include one or more blowers 816 and/or one or morecirculators 818. For example, in this embodiment, blower 816 is disposedin process air pathway 810 and is configured to adjust a flow rate ofair through the process air pathway. Circulator 818, in this embodiment,is disposed in regeneration fluid pathway 812 and is configured toadjust a flow rate of fluid through the regeneration fluid pathway. Insome embodiments, blower 816 and/or circulator 818 may be controlled bycontroller 820 (e.g., controlling a speed of blower 816 and/orcirculator 818 to optimize liquid water production). In someembodiments, blower 816 and/or circulator 818 may be configured tosubstantially maintain a pre-determined flow rate through process airpathway 810 and/or regeneration fluid pathway 812, respectively.

System 800 may comprise a thermal unit 822, configured to providethermal energy to fluid in regeneration fluid pathway 812 (e.g., suchthat desiccant unit 804 may be regenerated). Thermal unit 822 may be asolar thermal unit of the present technology, where the heat absorbingfluid 116, 516 (as shown in FIGS. 3 and 5) from the outlet 122, 522 (asshown in FIGS. 1 and 5) travels along the regeneration fluid pathway 812from the thermal unit 822 to the desiccant unit 804.

System 800 may comprise a condenser 824 configured to receive fluid fromthe desorption zone via the regeneration fluid pathway and produceliquid water from the received fluid (e.g., by condensing water vapor influid in the regeneration fluid pathway). Condensers 824 may compriseany suitable material and may be of any suitable configuration (e.g., tocondense water vapor in regeneration fluid into liquid water). Forexample, suitable condensers may comprise polymers, metals, and/or thelike. Condensers may be arranged to include coils, fins, plates,tortuous passages, and/or the like. Condenser 80 may be configured totransfer thermal energy from fluid in regeneration fluid pathway 812downstream of desiccant unit 804 to air in process air pathway 810upstream of desiccant unit 804 (e.g., such that air in process airpathway 810 may facilitate cooling of condenser 824). In someembodiments, condenser 824 may be cooled by ambient air.

System 800 may comprise a water collection unit 826 configured toreceive liquid water produced by condenser 824. Liquid water produced bythe condenser may be provided to water collection unit 826 by way ofgravity; however, in other embodiments, flow of liquid water from thecondenser to the water collection unit may be assisted (e.g., by one ormore pumps, any other suitable delivery mechanism, and/or the like).

System 800 may comprise a filter 828 (e.g., a filtration membrane),which may be positioned between condenser 824 and water collection unit826 (e.g., to reduce an amount of impurities, such as, for example,sand, bacteria, fibrous, carbonaceous species, and/or the like, whichmay be present in liquid water produced by condenser 824).

Water collection unit 826 (e.g., or filter 828 thereof) may comprise anultraviolet (UV) light source (e.g., for disinfection of water producedby condenser 826). In some embodiments, suitable light sources maycomprise light emitting diodes (LEDs) having, for example: wavelengthsbelow 400 nanometers (nm) (e.g., 385 nm, 365 nm, and/or the like),wavelengths below 300 nm (e.g., 265 nm), and/or the like.

Water collection unit 826 may comprise one or more water level sensors(e.g., 902 of FIG. 11). Such water level sensors may compriseconductance sensors (e.g., open and/or closed circuit resistance-typeconductance sensors), which may operate via conductivity measurement ofwater in the range of 0.1 msiemens per cm.

Water collection unit 826 may comprise a receptacle 830 configured toreceive one or more additives for introduction to the produced liquidwater. Such additives may be configured to dissolve slowly into liquidwater stored in the water collection unit. Additives may include, butare not limited to, minerals, salts, other compounds, and/or the like.In some embodiments, additives may impart flavor to the produced liquidwater. For example, additives may include potassium salts, magnesiumsalts, calcium salts, fluoride salts, carbonate salts, iron salts,chloride salts, silica, limestone, and/or combinations thereof

System 800 may comprise indicators (e.g., lights, such as, for example,LEDs), which may be configured to provide information regarding systemoperation. For example, in some embodiments, indicator lights may beconfigured to provide information (e.g., visually, for example, to auser) that the system is running, that solar power (e.g., from powerunit 904) is available, that an air filter (e.g., within process airpathway 810) may need to be changed, that a water collection unit (e.g.,826) is full (e.g., in some embodiments, that the water collection unitcontains 20 L of liquid water), that an actuator (e.g., actuator 906,blower 816, circulator 818, and/or the like) has failed and/or isfailing, that telematics errors (e.g., as indicated by transceiver 908operation) have and/or are occurring, and/or the like. As describedbelow, any suitable information (including the information describedabove with reference to indicators) may be transmitted over acommunications network (e.g., alone and/or in addition to operation ofany indicators).

A controller (e.g., processor) 820 may control exposure of desiccantunit 804 (or a portion thereof) to air in process air pathway 810 andregeneration fluid in regeneration fluid pathway 812 (e.g., to increaseand/or optimize the liquid water ultimately produced by condenser 824),and such control may vary over a diurnal cycle (e.g., in response todiurnal variations). Such variations in environmental conditions (e.g.,inputs into controller 820) may include, for example, ambient airtemperature, ambient air relative humidity, and solar insolation. Otherinputs to controller 820 may include, for example, an amount of thermalenergy generated by thermal unit 822, a relative humidity of air inprocess air pathway 810, a relative humidity of fluid in regenerationfluid pathway 812, a temperature of fluid in the regeneration fluidpathway between desiccant unit 804 and thermal unit 822, a rate of waterproduction, and/or the like. In embodiments that include a purge airflowpath, inputs to controller 820 may include a flow rate, temperature,relative humidity and/or the like of air in the purge airflow path.Controller 820 may be configured to optimize liquid water production bycontrolling a rate of desiccant unit 804 movement between the adsorptionzone and the desorption zone, controlling a speed of blower 816 and/orcirculator 818, and/or the like, based, on measurements of one or moreof such inputs (e.g., such that controller 820 may optimize liquid waterproduction based on current environmental and system conditions). Asdescribed in more detail below, inputs to controller 820 may be measuredin that they are indicated in data captured by one or more sensors.

FIG. 11 is a diagram of an embodiment 900 of a system for generatingliquid water from air. System 900 may be substantially similar to system800, with the primary differences and/or additions described below.Otherwise, system 900 may comprise any and/or all features describedwith respect to system 800.

In system 900, as with system 800, desiccant 804 (or a first portionthereof) may be in fluid communication with process air in process airpathway 810 while the desiccant 804 (or a second portion thereof) issimultaneously in fluid communication with regeneration fluid inregeneration fluid pathway 812, and, thus, desiccant unit 802 operatesin a continuous and non-batch manner. In this embodiment, sections ofdesiccant 804 may be exposed to air in process air pathway 810 and fluidin regeneration fluid pathway 812 in an alternating manner.

System 900 may comprise a rotatable disk 910 (e.g., with desiccant 804disposed thereon). Desiccant 804 (or sections thereof) may be configuredto move between the adsorption zone and the desorption zone as disk 910is rotated. For example, in the depicted orientation of disk 910, aportion 912 of the desiccant is in communication with process airpathway 810, and a portion 914 of the disk is in communication withregeneration fluid pathway 812. System 900 may comprise an actuator(e.g., electrical motor) 906 configured to cause rotation of disk 910.Controller 820 may be configured to optimize liquid water production atleast by controlling movement (e.g., through control of actuator 906) ofdesiccant 804 (e.g., disk 910) between the adsorption zone and thedesorption zone. In other embodiments, actuator 906 may rotate disk 910at a predetermined rotation rate.

System 900 may comprise a solar power unit 904 configured to providepower to at least a portion of system 900 (e.g., blower 42, circulator46, actuator 114, and/or the like). Solar power unit 904 may beconfigured to convert solar insolation to electrical power (e.g., solarpower unit 904 comprises a solar panel). For example, solar power unit904 may be provided as a photovoltaic (PV) solar panel comprisingsemiconducting materials exhibiting a photovoltaic effect. In these andsimilar embodiments, controller 820 may be configured to control system900 in response to diurnal variations in solar insolation (e.g., anamount of electrical power generated by solar power unit 904). In someexamples, the solar power unit 904 may be PV panel 190 (as shown inFIGS. 1-2).

Systems for generating liquid water from air may be modular in nature.For example, systems may be configured such that each component (e.g.solar power unit 904, thermal unit 822, desiccant unit 802, condenser824, water collection unit 826, and/or the like) may be separated fromone another, transported, assembled and/or re-assembled with one another(e.g., in a same or a different configuration), and/or the like. Forexample, in some embodiments, the system may be configured such that nodimension of any singular component (e.g., water collection unit 826,desiccant unit 802, solar power unit 904, thermal unit 822, condenser824, and/or the like) is larger than six to eight feet (e.g., tofacilitate transport of the system or components thereof, for example,in a single cab truck bed, such as a bed of a Toyota Hilux pickup truck)(e.g., each component has a footprint that is less than or equal to 64square feet (ft²) and/or each component can be contained within a cubicvolume less than or equal to 512 cubic feet (ft³)).

Controller 820 may be configured to control one or more of blower 826,circulator 828, actuator 906, and/or the like (e.g., to optimize liquidwater production, where such control may be in response to diurnalvariations, for example, in ambient temperature, ambient air relativehumidity, solar insolation, and/or the like). For example, controller820 may be configured to increase a rate of liquid water production bycontrolling blower 826, circulator 828, actuator 906, and/or the like,taking into account, for example, diurnal variations. Such variationsmay change the amount of thermal energy generated by thermal unit 822,the level of electrical power provided by solar power unit 904, thelevel of humidity in process air entering the system, and/or the like.In some embodiments, ambient conditions may be measured in real-time orcan be forecast based on, for example, historical averages and/or thelike. In embodiments in which controller 820 receives real-timemeasurements, various sensors (described in more detail below) mayprovide data indicative of ambient conditions to controller 820 (e.g.,continuously, periodically, when requested by controller 820, and/or thelike).

Controller 820 may operate the system based on one or more of: a userselection, data received from one or more sensors, programmatic control,and/or by any other suitable bases. For example, controller 820 may beassociated with peripheral devices (including sensors) for sensing datainformation, data collection components for storing data information,and/or communication components for communicating data informationrelating to the operation of the system.

System 900 may comprise one or more peripheral devices, such as sensors902 and 916-922 (e.g., temperature sensors 916, humidity sensors 918,solar insolation sensor 920, flow rate sensors 922, water level sensor902, and/or the like). In some embodiments, one or more sensors mayprovide data indicative of ambient air temperature, ambient air relativehumidity, solar insolation, process air temperature, regeneration fluidtemperature, process air relative humidity, regeneration fluid relativehumidity, process air flow rate, regeneration fluid flow rate, liquidwater production rate, water usage rate, and/or the like.

One or more sensors 902 and 916-922 may be located remotely from othercomponents of the system and may provide captured data to the othercomponents of the system via a wired and/or wireless connection. Forexample, a town, village, city, and/or the like may include a pluralityof the present systems, and one of the plurality of the present systemsmay provide data indicative of ambient environmental conditions (e.g.,air temperature, air relative humidity, a solar insolation level, and/orthe like) to another one of the plurality of the present systems. Inthis way, in some embodiments, a single sensor may be shared by multiplesystems. In some embodiments, data communicated to a controller (e.g.,820) by one or more peripheral devices (e.g., one or more sensors 902 or916-922) may be stored in a data logging unit.

System 900 may comprise a telematics unit (e.g., a transmitter,receiver, transponder, transverter, repeater, transceiver, and/or thelike, sometimes referred to herein as “transceiver 908”). For example, atransceiver 908 may be configured to communicate data to and/or from thesystem (e.g., controller 820) via a wired and/or wireless interface(e.g., which may conform to standardized communications protocols, suchas, for example, GSM, SMS components operating at relatively low rates(e.g., operating every few minutes), protocols that may begeographically specified, and/or the like).

Transceiver 908 may be associated with a server and a communicationsnetwork for communicating information between the server and thetransceiver (e.g., and thus the system and/or a controller 820 thereof).Two-way communication may be facilitated by a cellular tower in cellularrange of the system. In some embodiments, a database (e.g., which may beremote from the system) may be configured to store information receivedfrom the server over the communications network.

In embodiments with telematics capability, a network administrator ordevice owner may send a command to controller 820 to update or deletelook-up table data (described below) and/or a control algorithm. In thisway, data security may be maintained, for example, in the case that thesystem is stolen or otherwise lost.

Controller 820 may be configured to vary operation of system 900 atleast based on real-time and/or forecast variations in ambientconditions. For example, controller 820 may control exposure ofdesiccant 804 (e.g., or sections thereof) to process air andregeneration fluid in response to changes in ambient conditions (e.g.,by changing the rotational speed of disk 910, such that the time that aportion of desiccant 804 disposed thereon is exposed to process air inprocess air pathway 810 or regeneration fluid in regeneration fluidpathway 812 may be increased or decreased). In some embodiments,controller 820 may be configured to vary a size of an adsorption zone ora desorption zone (e.g., in response to diurnal variations).

From the foregoing, it will be appreciated that although specificexamples have been described herein for purposes of illustration,various modifications may be made without deviating from the scope ofthis disclosure. It is therefore intended that the foregoing detaileddescription be regarded as illustrative rather than limiting, and thatit be understood that it is the following claims, including allequivalents, that are intended to particularly point out and distinctlyclaim the claimed subject matter.

What is claimed is:
 1. A solar thermal unit comprising: a glazing layer;a first porous light absorbing material layer disposed below and spacedapart from the glazing layer; a first interstitial layer disposedbetween the glazing layer and the first porous light absorbing materiallayer; and, a first fluid flow path configured to direct a regenerationfluid between an inner surface of the glazing layer and a top surface ofthe first interstitial layer and then through the first porous lightabsorbing material layer; wherein the regeneration fluid is configuredto collect heat from the glazing layer, and then from the first porouslight absorbing material layer.
 2. The solar thermal unit of claim 1,wherein the first interstitial layer is disposed above and spaced apartfrom a top surface of the first porous light absorbing material layer;and, wherein the first fluid flow path is configured to direct theregeneration fluid along a bottom surface of the first interstitiallayer in advance of flow through the first porous light absorbingmaterial layer.
 3. The solar thermal unit of claim 1, wherein the firstinterstitial layer comprises a photovoltaic panel.
 4. The solar thermalunit of claim 3, wherein the first fluid flow path is configured todirect the regeneration fluid to collect heat from both the top surfaceand the bottom surface of the PV panel in advance of flow through thefirst porous light absorbing material layer.
 5. The solar thermal unitof claim 3, wherein at least one surface of the photovoltaic panel ismodified to promote flow interaction with the photovoltaic panel.
 6. Thesolar thermal unit of claim 1, wherein the solar thermal unit furthercomprises: a second porous light absorbing material layer disposed belowand spaced apart from the glazing layer; a second interstitial layerdisposed between the glazing layer and the second porous light absorbingmaterial layer; a second fluid flow path configured to direct a portionof the regeneration fluid along an inner surface of the glazing layerand a top surface of the second interstitial layer in advance of flowthrough the second porous light absorbing material layer; and, whereinthe solar thermal unit is configured to distribute the regenerationfluid between the first fluid flow path and the second fluid flow path;wherein the regeneration fluid in the second fluid flow path isconfigured to collect heat first from the glazing layer, and then fromthe second porous light absorbing material layer.
 7. The solar thermalunit of claim 6, wherein at least one of the first interstitial layerand the second interstitial layer comprises at least one of aphotovoltaic panel and a glazing.
 8. The solar thermal unit of claim 6,wherein the first fluid flow path is configured to direct theregeneration fluid: between the glazing layer and the first interstitiallayer, through a first transition disposed between the firstinterstitial layer and the second interstitial layer, between the firstinterstitial layer and the first porous light absorbing material layer,and through the first porous light absorbing material layer.
 9. Thesolar thermal unit of claim 9 wherein, within the first transition, theregeneration fluid of the first fluid flow path intermingles with theregeneration fluid of the second fluid flow path.
 10. A solar thermalunit of a water generation system comprising: a glazing layer; a firstporous light absorbing material layer disposed below and spaced apartfrom the glazing layer, a photovoltaic panel configured to provide powerto the water generation system; a regeneration fluid flow pathconfigured to direct a regeneration fluid along an inner surface of theglazing layer and at least a first surface of the photovoltaic panelbefore flowing through the first porous light absorbing material layer;wherein the regeneration fluid is configured to collect heat from theglazing layer and the photovoltaic panel in advance of flowing throughthe first porous light absorbing material layer.
 11. The solar thermalunit of claim 10, further comprising: a first interstitial layerdisposed between the glazing layer and the first porous light absorbingmaterial layer.
 12. The solar thermal unit of claim 11, wherein thefirst interstitial layer comprises a glazing and the photovoltaic panel.13. The solar thermal unit of claim 10, further comprising a plenumincluding the photovoltaic panel.
 14. A water generation systemcomprising: a solar thermal unit comprising: a glazing layer; a firstporous light absorbing material layer disposed below and spaced apartfrom the glazing layer; a first interstitial layer disposed between theglazing layer and the first porous light absorbing material layer; aregeneration flow path configured to direct a regeneration fluid betweenan inner surface of the glazing layer and a top surface of the firstinterstitial layer in advance of flowing through the first porous lightabsorbing material layer; a desiccant in fluid communication with theregeneration flow path; a circulator configured to adjust a flow rate ofthe regeneration fluid in the regeneration flow path; and, a condenserconfigured to receive the regeneration fluid from the solar thermal unitvia the regeneration flow path and condense water vapor in the receivedregeneration fluid to produce liquid water; wherein the regenerationfluid collects heat from the glazing layer in advance of flowing throughthe porous light absorbing material layer before being received by thecondenser.
 15. The water generation system of claim 14, furthercomprising a photovoltaic panel configured to power the water generationsystem including the circulator.
 16. The water generation system ofclaim 15, wherein the first interstitial layer comprises thephotovoltaic panel.
 17. The water generation system of claim 15, furthercomprising a controller configured to control the speed of thecirculator based on an amount of electrical power generated by thephotovoltaic panel.
 18. The water generation system of claim 14, furthercomprising a controller configured to control the water generationsystem in response to diurnal variations in solar insolation.
 19. Thewater generation system of claim 14, wherein the desiccant is combinedwith thermal radiation absorbing materials.
 20. The water generationsystem of claim 14, wherein the solar thermal unit is configured todistribute the regeneration fluid between a plurality of sub-flow pathsof the regeneration flow path to balance the pressure drop across thesolar thermal unit.